How much CO2 is produced from a gallon of petrol?
It seems improbable that a gallon of petrol, which weighs about 7.4lbs, could produce 23 pounds of CO2 when burned. However, most of the weight of the CO2 doesn't come from the petrol itself, but from the oxygen in the air.
When petrol burns, the carbon and hydrogen separate. The hydrogen combines with oxygen to form water (H2O), and carbon combines with oxygen to form CO2. A carbon atom has a weight of 12 and each oxygen atom has a weight of 16, giving each single molecule of CO2 an atomic weight of 44 (12 from carbon and 32 from oxygen). To calculate the amount of CO2 produced from a gallon of petrol, the weight of the carbon in the petrol is multiplied by 44/12 or about 3.7.
Since petrol is about 87% carbon and 13% hydrogen by weight, the carbon in a gallon of petrol weighs 6.4lbs. (7.4lbs x 0.87).
We can then multiply the weight of the carbon (6.4lbs) by 3.7, which equals 23.6lbs of CO2!
Metric calculation.
